DEAR DR. ROACH: I’m female, 68 years old with hypothyroidism but no other medical problems. I exercise about 10 hours a week and try to eat healthy. During one of my physical checkups, my TSH was 0.002, so I saw an endocrinologist. After three months of blood tests, everything became normal even without medicine. My T4, T3, TSH and complete metabolic panel results all are in the normal range. The one that is not is the TPO level, which is greater than 600. She asked me to take 25 mcg of levothyroxine once a day. When I asked her if I need to continue the medication, she said yes, because of the presence of TPO. Is it true that once you have TPO, you have it for life and it won’t go away? Will I have to take the medicine for life? — C.G.

ANSWER: There’s a lot of information here, but let’s start with the TPO (really, anti-TPO), which are antibodies to the enzyme thyroid peroxidase. High levels of anti-TPO are suggestive of Hashimoto’s thyroiditis. A low TSH, such as the 0.002 you initially had, is highly suggestive of hyperthyroidism. Right now, you are not hypothyroid.

Over time, the thyroid usually returns to normal, but this can take years.

Someone with no thyroid due to surgery needs full replacement, which is somewhere around 125 mcg, though it varies from person to person.